I did what Big John is doing & working fine so far. I'll let him tell you as it's his idea / process on the cylinder o'rings that I copied. This is my first 880 build.
On the 860 never changed anything on series 3 or the R motor. No problems but then I don't have a problem with detonation with my head designs either.

Well we're still figuring things out and new engine build etc.
I started out with the same clutching I've been running for several years so as to have a baseline to compare to but in the meantime I went to a different track and belt drive and geared up to 2.3 . That seems to have tipped the apple cart over! Used to be at 2.47.

My best set up has been 72 grms.+- running Thunder arms. That equates to somewhere between 19.7 and 21 grms in the pins alone, stock rollers, 433 ramps laid down .060" with a 100X260 spring up to 6,000 feet which is about it for up here in Valdez. This is at 8,250 rpm+-.
I run very little twist in the Paragon with the AC snow pro spring, maybe 1/8" to 1/4" max. Being at 55* finish that's all I've needed. Lately been running 60*X55* helix. Been running 58*X55* for several years but didn't have another helix like that for this sled so went with what I had. Can't notice any difference as far as the helix goes. Ran straight 58* in Summits for years but as I made more power couldn't hang on to the belt and so ended up at 55*. Any less than 58* start and big bores are too "buzzy".
We'll see>>>>>

880 I had I ran 100/230
11 grams and a 415-441 blended ramp. 415 only for the first portion .
63/55 helix with cat yellow when I was using the older Paragon.
The newer ones with reverse cut into towers only need compression springs.
2:52 ration with belt drive and 174 track

Interesting. That would be a really nice set up when it matched conditions.
Can't run that low of gearing as I would be wayyy up in overdrive. I'm at 2.3 and it's border line too low. Shame because I love low gearing, but I don't like to get in overdrive in the steep pulls.
I've been going to try less helix angle with a wimpy spring to try and drop some weight in the drive. Haven't got to it yet.
You can still run torsion spring with reverse cut towers. That's what I run in my trail sled. I don't like the compression spring set up. Ran it, no comparison.
TRA stalls the shift when you get to a point in top end with 441 and similar ramps. Arm loses leverage when it climbs too high. Ran 2 mm oversize rollers for years that worked but couldn't keep bushings in them. 417 ramp finished same place as 415 with 2 mm over rollers. Ground the bottom end too try & load big bores. Gave up!!!
433 ramp dropped .060" is approx same as 417 finish only with nice low engagement and HUGE bottom-mid up shift. Great big bore ramp and actually have run 433 in several little race sleds 440's and 600 mods. Just alter them to fit power curve & hold on! These were all with Paragons.

Getting quite the education here.
For what it's worth, anyone wanting to try big Lectrons on Skidoo, the Boyeson 600 SDI reeds for rev chassis are a really good match.
They flow the same as 46 Lectrons and after experimenting with different petals am back to the ones that came with!!!! Was running stiffer petals in the Boyesons' but it flat didn't like it. I was all over the place with the fueling trying to make it happy, no go. Put the stock petals back in = oh yea!!!!!!!!!!!
We're making headway, had to modify airbox again, but it was worth it because it flat out is moving some air now! Had to change pipe restrictors / adjust to get pipe pressure back down.

Things really coming together now. Pipes are dialed in & fueling getting close enough to finish breaking in. Motor is starting to really wake up. I went ahead and pulled a degree of timing back out of it and is probably where I'll run it now. I don't think I was getting enough heat in these big twins. Made one last test pull here at home and then was heading up the mountain, I thought!
Then it started going through the belts in the belt drive. Went through the whole chassis measuring / checking. Everything is dead nuts straight. As much as I hate to do it, putting the chain case back on. I'm not going to do the extra 2 or 3 belts in the back pack thing. I know I can get by running a chain, so I'm going back to what I know works. I suspect I'm getting too much flex / things moving around to run the C3 on a Rev? Dang>>>>>>